Table 1.

Baseline characteristics

Variable	CEA ≤ ULN N = 604	CEA > ULN N = 121	p value	CA 19.9 ≤ ULN N = 531	CA 19.9 > ULN N = 168	p value
CEA/CA 19-9 level in µg/L/kU/L Median (range)	CEA level 2 (0–1533)			CA 19-9 level 11 (0–15,429)
Age in years			0.987			0.182
< 60	243 (40%)	48 (40%)		222 (42%)	61 (36%)
60–69	230 (38%)	46 (38%)		201 (38%)	62 (37%)
≥ 70	131 (22%)	27 (22%)		108 (20%)	45 (27%)
Sex			0.001
Male	391 (65%)	97 (80%)		356 (67%)	117 (70%)
Female	213 (35%)	24 (20%)		175 (33%)	51 (30%)	0.530
WHO PS			0.004			0.004
Missing	33	8		25	15
0	420 (74%)	68 (60%)		375 (74%)	95 (62%)
1	151 (26%)	45 (40%)		131 (25%)	58 (38%)
Lauren classification (biopsy)			0.009			0.048
Intestinal	177 (29%)	51 (42%)		164 (31%)	56 (33%)
Diffuse	195 (32%)	23 (19%)		170 (32%)	38 (23%)
Mixed	35 (6%)	7 (6%)		26 (5%)	15 (9%)
Unknown	197 (33%)	40 (33%)		171 (32%)	59 (35%)
Tumor localization			< 0.001			0.002
GEJ	95 (16%)	37 (31%)		84 (16%)	44 (26%)
Proximal	119 (20%)	28 (23%)		104 (20%)	41 (24%)
Middle	190 (32%)	23 (19%)		159 (30%)	43 (26%)
Distal	200 (33%)	33 (27%)		184 (35%)	40 (24%)
BMI			0.084			0.543
≥ 30	84 (14%)	14 (12%)		69 (13%)	23 (14%)
25–30	220 (36%)	39 (32%)		187 (35%)	63 (38%)
18.5–25	289 (48%)	61 (50%)		264 (50%)	76 (45%)
≤ 18.5	11 (2%)	7 (6%)		11 (2%)	6 (4%)
BMI			0.028			0.985
Median (IQR)	25 (23–28)	25 (22–27)		25 (23–28)	25 (23–28)
Allocated treatment			0.703			0.011
Postop CT	303 (50%)	63 (48%)		253 (48%)	99 (59%)
Postop CRT	301 (50%)	58 (52%)		278 (52%)	69 (42%)
CA 19-9 or CEA level*	Missing n = 28	Missing n = 6	< 0.001	Missing n = 7	Missing n = 2	< 0.002
≤ ULN	461 (80%)	63 (55%)		461 (88%)	114 (69%)
> ULN	114 (20%)	52 (45%)		63 (12%)	52 (31%)

CA 19-9 carbohydrate antigen 19-9, CEA carcinoembryonic antigen, postop postoperative, CRT chemoradiotherapy, CT chemotherapy

^*ULN for CEA was 6 µg/L, ULN for CA 19-9 was ≤ 37 kU/L